Preheat oven to 425 degrees F.
Place flank steak on a sheet pan.
In a small bowl mix together the "Steak Sauce" ingredients: oyster sauce, soy sauce, garlic powder, minced garlic, sesame oil, and corn starch, and whisk until smooth.
Pour over flank steak, and spread evenly over the top.
Bake for 15-17 minutes depending on the thickness of the steak.
Meanwhile, mix together sauce ingredients in a medium sized bowl, whisking until smooth.
When time is up, remove steak from oven, and slice into super thin slices, against the grain (this will help it be tender).
Return steak and any juices to the pan.
Dump broccoli over the top of the steak.
Pour sauce over the top of all of it, and stir to mix it all together.
Return to 425 degree F oven, and bake an additional 5-8 minutes until broccoli is fork tender.
Remove from oven. top with sesame seeds, stir well to coat everything in sauce.
Serve over jasmine rice, and spoon some of the pan sauce over the top if you wish.